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Subject[PATCH 06/14] eeprom: at24: split at24_eeprom_read() into specialized functions
Date
Split at24_eeprom_read() into two smaller functions - one for the
i2c operations and one for the smbus extensions. Assign them in
at24_probe() depending on the bus capabilities.

Also: in order to avoid duplications move the comments related to
offset calculations above the at24_translate_offset() routine.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
drivers/misc/eeprom/at24.c | 125 +++++++++++++++++++++++++--------------------
1 file changed, 71 insertions(+), 54 deletions(-)

diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index 2efb572..e7db137 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -165,6 +165,19 @@ MODULE_DEVICE_TABLE(acpi, at24_acpi_ids);
* This routine supports chips which consume multiple I2C addresses. It
* computes the addressing information to be used for a given r/w request.
* Assumes that sanity checks for offset happened at sysfs-layer.
+ *
+ * Slave address and byte offset derive from the offset. Always
+ * set the byte address; on a multi-master board, another master
+ * may have changed the chip's "current" address pointer.
+ *
+ * REVISIT some multi-address chips don't rollover page reads to
+ * the next slave address, so we may need to truncate the count.
+ * Those chips might need another quirk flag.
+ *
+ * If the real hardware used four adjacent 24c02 chips and that
+ * were misconfigured as one 24c08, that would be a similar effect:
+ * one "eeprom" file not four, but larger reads would fail when
+ * they crossed certain pages.
*/
static struct i2c_client *at24_translate_offset(struct at24_data *at24,
unsigned int *offset)
@@ -182,74 +195,77 @@ static struct i2c_client *at24_translate_offset(struct at24_data *at24,
return at24->client[i];
}

-static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
- unsigned int offset, size_t count)
+static ssize_t at24_eeprom_read_smbus(struct at24_data *at24, char *buf,
+ unsigned int offset, size_t count)
{
- struct i2c_msg msg[2];
- u8 msgbuf[2];
+ unsigned long timeout, read_time;
struct i2c_client *client;
+ int status;
+
+ client = at24_translate_offset(at24, &offset);
+
+ if (count > io_limit)
+ count = io_limit;
+
+ /* Smaller eeproms can work given some SMBus extension calls */
+ if (count > I2C_SMBUS_BLOCK_MAX)
+ count = I2C_SMBUS_BLOCK_MAX;
+
+ loop_until_timeout(timeout, read_time) {
+ status = i2c_smbus_read_i2c_block_data_or_emulated(client,
+ offset,
+ count, buf);
+
+ dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
+ count, offset, status, jiffies);
+
+ if (status == count)
+ return count;
+ }
+
+ return -ETIMEDOUT;
+}
+
+static ssize_t at24_eeprom_read_i2c(struct at24_data *at24, char *buf,
+ unsigned int offset, size_t count)
+{
unsigned long timeout, read_time;
+ struct i2c_client *client;
+ struct i2c_msg msg[2];
int status, i;
+ u8 msgbuf[2];

memset(msg, 0, sizeof(msg));
-
- /*
- * REVISIT some multi-address chips don't rollover page reads to
- * the next slave address, so we may need to truncate the count.
- * Those chips might need another quirk flag.
- *
- * If the real hardware used four adjacent 24c02 chips and that
- * were misconfigured as one 24c08, that would be a similar effect:
- * one "eeprom" file not four, but larger reads would fail when
- * they crossed certain pages.
- */
-
- /*
- * Slave address and byte offset derive from the offset. Always
- * set the byte address; on a multi-master board, another master
- * may have changed the chip's "current" address pointer.
- */
client = at24_translate_offset(at24, &offset);

if (count > io_limit)
count = io_limit;

- if (at24->use_smbus) {
- /* Smaller eeproms can work given some SMBus extension calls */
- if (count > I2C_SMBUS_BLOCK_MAX)
- count = I2C_SMBUS_BLOCK_MAX;
- } else {
- /*
- * When we have a better choice than SMBus calls, use a
- * combined I2C message. Write address; then read up to
- * io_limit data bytes. Note that read page rollover helps us
- * here (unlike writes). msgbuf is u8 and will cast to our
- * needs.
- */
- i = 0;
- if (at24->chip.flags & AT24_FLAG_ADDR16)
- msgbuf[i++] = offset >> 8;
- msgbuf[i++] = offset;
+ /*
+ * When we have a better choice than SMBus calls, use a combined I2C
+ * message. Write address; then read up to io_limit data bytes. Note
+ * that read page rollover helps us here (unlike writes). msgbuf is
+ * u8 and will cast to our needs.
+ */
+ i = 0;
+ if (at24->chip.flags & AT24_FLAG_ADDR16)
+ msgbuf[i++] = offset >> 8;
+ msgbuf[i++] = offset;

- msg[0].addr = client->addr;
- msg[0].buf = msgbuf;
- msg[0].len = i;
+ msg[0].addr = client->addr;
+ msg[0].buf = msgbuf;
+ msg[0].len = i;

- msg[1].addr = client->addr;
- msg[1].flags = I2C_M_RD;
- msg[1].buf = buf;
- msg[1].len = count;
- }
+ msg[1].addr = client->addr;
+ msg[1].flags = I2C_M_RD;
+ msg[1].buf = buf;
+ msg[1].len = count;

loop_until_timeout(timeout, read_time) {
- if (at24->use_smbus) {
- status = i2c_smbus_read_i2c_block_data_or_emulated(client, offset,
- count, buf);
- } else {
- status = i2c_transfer(client->adapter, msg, 2);
- if (status == 2)
- status = count;
- }
+ status = i2c_transfer(client->adapter, msg, 2);
+ if (status == 2)
+ status = count;
+
dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
count, offset, status, jiffies);

@@ -520,7 +536,8 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
at24->chip = chip;
at24->num_addresses = num_addresses;

- at24->read_func = at24_eeprom_read;
+ at24->read_func = at24->use_smbus ? at24_eeprom_read_smbus
+ : at24_eeprom_read_i2c;
at24->write_func = at24_eeprom_write;

writable = !(chip.flags & AT24_FLAG_READONLY);
--
2.7.4
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